Method and apparatus for setting handover parameter in mobile communication system

ABSTRACT

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). A method of setting a handover parameter includes receiving, from a serving evolved NodeB (eNB), cell type information indicating eNB types of the serving eNB and eNBs adjacent to the serving eNB, and mobility information of the UE, detecting types of the serving eNB and a target eNB based on the cell type information, and setting a Time-To-Trigger (TTT) applied, the mobility information of the UE, and a received signal strength for the serving eNB.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/133,145, filed on Sep. 17, 2018, which is a continuationapplication of prior application Ser. No. 14/605,401, filed on Jan. 26,2015, which has issued as U.S. Pat. No. 10,080,167 on Sep. 18, 2018 andwas based on and claimed priority under 35 U.S.C § 119(a) of a Koreanpatent application number 10-2014-0009247, filed on Jan. 24, 2014, inthe Korean Intellectual Property Office, the disclosure of which isincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to a method and an apparatus for settinga handover parameter considered when a handover is performed in a mobilecommunication system.

BACKGROUND

To meet the demand for wireless data traffic having increased sincedeployment of 4G (4^(th)-Generation) communication systems, efforts havebeen made to develop an improved 5G (5^(th)-Generation) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

A handover refers to the change of a service evolved Node B (eNB) fromwhich a User Equipment (UE) receives a current service into an eNB whichcan provide better service. For example, when service qualitydeteriorates while the UE receives the service from the serving eNB, thehandover to a target eNB which can provide better service is made andthe UE continuously receives the service from the target eNB.

FIGS. 1A and 1B illustrate examples of a heterogeneous network includinga macro eNB and a small eNB according to the related art.

Referring to FIG. 1A, it is assumed that a heterogeneous networkincludes a plurality of cells, and each of the cells includes one macroeNB 105, 107, 109, and 111, and one or more small eNBs 113, 117, 119,121, 123, 125, and 127. The small eNB may be, for example, a micro eNB,a pico eNB, or a femto eNB.

UEs 101 and 103 moving within an illustrated communication area 100perform a handover to maintain the quality of service which the UEsreceive.

When it is assumed that a serving eNB is the macro eNB 105, the UE mayperform a handover from the macro eNB 105 to the macro eNB 107 or thesmall eNB 117 according to a movement position. When it is assumed thata serving eNB is the small eNB 117, the UE may perform a handover fromthe small eNB 117 to the small eNB 119 or the macro eNB 107 according toa movement position.

Referring to FIG. 1B, a graph illustrates a downlink received signalstrength of the UE with respect to a distance between the macro eNB andthe small eNB included in the heterogeneous network. Specifically, inFIG. 1B, a horizontal axis of the illustrated graph indicates a distancebetween the macro eNB 100 and the small eNB 120 and a vertical axisindicates a downlink received signal strength of the UE 130. That is,reference numeral 160 indicates a downlink received signal strength withrespect to the macro eNB 110 and reference numeral 170 indicates adownlink received signal strength with respect to the small eNB 120.Further, reference numeral 140 indicates a macro eNB communication areain which data transmission/reception to/from the macro eNB 110 ispossible, and reference numeral 150 indicates a small eNB communicationarea in which data transmission/reception to/from the small eNB 120 ispossible.

As described above, in the heterogeneous network including the macroeNBs and the small eNBs, the UE may perform a handover from the macroeNB to the macro eNB, a handover from the macro eNB to the small eNB, ahandover from the small eNB to the macro eNB, or a handover from thesmall eNB to the small eNB. For an efficient handover in theheterogeneous network, a method of adaptively applying a handoverparameter according to types of a serving eNB and a target eNB isrequired.

However, at present no method has been prepared to adaptively apply thehandover parameter according to the type of a serving eNB and a targeteNB in the heterogeneous network.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and an apparatus for setting ahandover parameter in consideration of the type of a serving evolvedNode B (eNB) and a target eNB in a mobile communication system.

Another aspect of the present disclosure is to provide a method and anapparatus for setting a handover parameter in consideration of amovement speed of a User Equipment (UE) in a mobile communicationsystem.

In accordance with an aspect of the present disclosure, a method ofsetting a handover parameter by a UE in a mobile communication system isprovided. The method includes: receiving, from a serving evolved Node B(eNB), cell type information and mobility information of the UE, thecell type information indicating eNB types of the serving eNB and eNBsadjacent to the serving eNB, detecting a serving eNB type and a targeteNB type based on the cell type information, and setting aTime-To-Trigger (TTT) applied if a handover event is detected based onthe serving eNB type, the target eNB type, the mobility information ofthe UE, and a received signal strength for the serving eNB, wherein theTTT is set as a short TTT or a long TTT, and wherein the short TTT isless than a preset value and the long TTT is greater than or equal tothe preset.

In accordance with another aspect of the present disclosure, a UEsetting a handover parameter in a mobile communication system isprovided. The UE includes a receiver configured to receive, from aserving eNB, cell type information indicating eNB types of the servingeNB and eNBs adjacent to the serving eNB, and mobility information ofthe UE, and a controller configured to detect a serving eNB type and atarget eNB type based on the cell type information, and to set aTime-To-Trigger (TTT) applied if a handover event is detected based onthe serving eNB type, the target eNB type, the mobility information ofthe UE, and a received signal strength for the serving eNB, wherein theTTT is set as a short TTT or a long TTT, and wherein the short TTT isless than a preset value and the long TTT is larger than or equal to thepreset value.

According to the present disclosure, a UE can set a handover parameterconsidered when a handover is performed based on the type of a servingeNB and a target eNB, and a UE movement speed, and more particularly,can improve handover efficiency and more stably provide better serviceto the UE by adaptively setting a time parameter considered when ahandover event is detected.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1A and 1B illustrate examples of a heterogeneous network includinga macro evolved Node B (eNB) and a small eNB according to the relatedart;

FIG. 2 illustrates an example of a handover process performed by a UserEquipment (UE) in a mobile communication system according to anembodiment of the present disclosure;

FIG. 3 is a graph showing a DownLink (DL) received signal strengthaccording to a UE position when a handover of the UE from a macro eNB toanother macro eNB is made in a mobile communication system according toan embodiment of the present disclosure;

FIG. 4 is a graph showing a DL received signal strength according to aUE position when a handover of the UE from a macro eNB to a small eNB ismade in a mobile communication system according to an embodiment of thepresent disclosure;

FIG. 5 illustrates an example flow diagram in which an eNB provides ahandover parameter to a UE in a mobile communication system according toan embodiment of the present disclosure;

FIG. 6 is a flowchart illustrating an example in which a UE adaptivelysets a Time-To-Trigger (TTT) according to an embodiment of the presentdisclosure;

FIGS. 7A and 7B illustrate examples in which a UE uses a short TTT and along TTT in a mobile communication system according to variousembodiments of the present disclosure;

FIG. 8 is a flowchart illustrating an example in which a UE switches apreset long TTT to a short TTT in a mobile communication systemaccording to an embodiment of the present disclosure;

FIG. 9 is a flowchart illustrating an example in which a UE switches apreset short TTT to a long TTT in a mobile communication systemaccording to an embodiment of the present disclosure; and

FIGS. 10A and 10B illustrate examples in which a UE switches a currentlyapplied TTT in a mobile communication system according to variousembodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

FIG. 2 illustrates an example of a handover process performed by a UserEquipment (UE) in a mobile communication system according to anembodiment of the present disclosure.

Referring to FIG. 2, it is assumed that the communication systemcorresponds to, for example, a Long Term Evolution-Advanced (LTE-A)communication system and an LTE-A communication system includes a UE200, a source evolved Node B (eNB) 210, and a target eNB 220. The sourceeNB 210 refers to a serving eNB from which the UE 200 currently receivesservice.

The UE 200 receives a measurement control message from each of thesource eNB 210 and the target eNB 220 in operations 201 and 202. The UE200 measures DownLink (DL) signal strengths for the source eNB 210 andthe target eNB 220 and detects a handover event through the measured DLsignal strengths in operation 203.

The handover event means that a state, in which a DL signal strength orsignal quality of the target eNB is higher (or better) than a DL signalstrength or signal quality of the serving eNB by a predetermined offset,is maintained for a predetermined time. That is, the handover eventmeans that a state, in which

Reference Signal Received Power (RSRP) for the target eNB RSRPtarget islarger than a sum of RSRP for the serving eNB RSRP serving and apredetermined offset A (RSRPtarget>RSRPserving+A), or a state, in whichReference Signal Received Quality (RSRQ) for the target eNB RSRQtargetis larger than a sum of RSRQ for the serving eNB RSRQserving and apredetermined offset A (RSRQtarget>RSRQserving+A), is maintained forTime-To-Trigger (TTT).

The UE 200 having detected the handover event in which the state wherethe RSRP or RSRQ of the target eNB 220 is higher (or better) than theRSRP or RSRQ of the source eNB 210 by A is maintained for the TTT inoperation 203 receives UpLink (UL) resources from the source eNB 210 inoperation 205. Thereafter, the UE transmits a measurement report messageto the source eNB 210 in operation 207 to inform the source eNB 210 ofthe detection of the handover event.

The source eNB 210 determines whether to perform the handover of the UE200 in operation 209. When there is a determination to perform thehandover of the UE 200 in operation 209, the source eNB 210 transmits ahandover request message to the target eNB 220 in operation 211.

The target eNB 220 determines whether to perform the handover through anadmission control in operation 213, and transmits a response message 215of a handover request message to the source eNB 210 in operation 215.Here, it is assumed that the target eNB 220 accepts the handoverrequest. In this case, the handover response message includes anAcknowledge (ACK) message.

The source eNB 210 having received the ACK message for accepting thehandover request allocates DL resources to the UE 200 in operation 217,and transmits a handover command message to the UE 200 in operation 219.The handover command message includes information required forperforming the handover.

The UE 200 performs the remaining handover operations based on theinformation included in the handover command message. That is, the UE200 acquires synchronization with the target eNB 220 and accesses aRandom Access CHannel (RACH) in operation 221, receives UL resourcesfrom the target eNB 220 in operation 223, and transmits a handoverconfirm message to the target eNB 220 in operation 225.

Operations 207 to 217 described above are included in a handoverpreparation phase 230, and operations 219 to 225 are included in ahandover execution phase 240. After the handover execution phase 240 iscompletely performed, in operation 227, the source eNB 210 releases theallocated resources in operations 205 and 217.

Meanwhile, in order to successfully perform the handover, communicationshould be performed between the source eNB (or serving eNB) 210 and theUE 200, between the source eNB 210 and the target eNB 220, and betweenthe target eNB 220 and the UE 200, and the communication requires apredetermined time or longer. Particularly, since the handover is mainlygenerated when the UE 200 moves away from the source eNB 210 and becomescloser to the target eNB 220, it is important for the UE 200 to receivethe handover command message from the source eNB 210 before a channelgain between the UE 200 and the source eNB 210 becomes lower.

However, when a predetermined time considered when the handover event isdetected, that is, the TTT is set as a time which is too long, a delayis generated in the handover, and thus the channel gain between the UE200 and the source eNB 210 becomes lower. Accordingly, the UE 200 maynot successfully receive the handover command message transmitted fromthe source eNB 210.

In contrast, when the TTT considered when the handover event is detectedis set as a time which is too short, there is not enough time to monitorthe channel gain between the source eNB 210 and the target eNB 220.Accordingly, a ping-pong phenomenon in which unnecessary handovers arerepeated between the source eNB 210 and the target eNB 220 is generated.Therefore, it is very important to set the TTT as a proper value toperform a more efficient handover.

Hereinafter, the reason why the TTT should be set as a proper value willbe described in more detail with reference to FIGS. 3 and 4.

FIG. 3 is a graph showing a DL received signal strength according to aUE position when a handover of the UE from a macro eNB to another macroeNB is made in a mobile communication system according to an embodimentof the present disclosure.

Referring to FIG. 3, a horizontal axis of the graph indicates a positionof the UE and a vertical axis indicates a DL received signal strength ofthe UE. Further, reference numeral 300 indicates a DL received signalstrength with respect to a first macro eNB, for example, received powerP1, and reference numeral 310 indicates a DL received signal strengthwith respect to a second macro eNB, for example, received power P2.

The UE detects that a difference between P1 and P2 is larger than orequal to a predetermined threshold (P1-P2≥threshold) in a correspondingposition 301, and identifies whether the state (P1-P2≥threshold) ismaintained in a predetermined time, that is, the TTT. When the state(P1-P2≥threshold) is maintained for the TTT, the UE transmits ameasurement report message to the first macro eNB corresponding to theserving eNB in a corresponding position 303 and receives a handovercommand message from the first macro eNB in a corresponding position305. Thereafter, the UE determines that the handover is successful basedon the reception of the handover command message.

FIG. 4 is a graph showing a DL received signal strength according to aUE position when a handover of the UE from a macro eNB to a small eNB ismade in a mobile communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 4, a horizontal axis of the graph indicates a positionof the UE and a vertical axis indicates a DL received signal strength ofthe UE. Further, reference numeral 400 indicates a DL received signalstrength with respect to the macro eNB, for example, received power P 1,and reference numeral 410 indicates a DL received signal strength withrespect to the small eNB, for example, received power P2.

The UE detects that a difference between P1 and P2 is larger than orequal to a predetermined threshold (P1-P2≥threshold) in a correspondingposition 401, and identifies whether the state (P1-P2≥threshold) ismaintained in a predetermined time, that is, the TTT. It is assumed thatthe TTT is the same as the TTT applied to FIG. 3. When the state(P1-P2≥threshold) is maintained for the TTT, the UE transmits ameasurement report message to the macro eNB corresponding to the servingeNB in a corresponding position 403 and receives a handover commandmessage from the macro eNB in a corresponding position 405.

However, since the DL received signal strength of the small eNB in thecorresponding position 405, the DL received signal from the small eNBacts as significantly large interference when the UE receives thehandover command message transmitted from the macro eNB. Due to theinterference, the UE has a difficulty in successfully receiving thehandover command message transmitted from the macro eNB, and a UE whichhas not received the handover command message in the position 405 failsto perform the handover. In this case, in order not to fail to performthe handover, a method of performing handover before an increase ininterference from the small eNB may exist as one solution. To this end,the TTT corresponding to the parameter considered when the handoverevent is detected should be set as a value smaller than the TTT appliedto FIG. 3.

Further, in the heterogeneous network including the macro eNB and thesmall eNB, not only the handover between macro eNBs but also a handoverfrom a macro eNB to a small eNB, a handover from a small eNB to a macroeNB, or a handover from a small eNB to another small eNB may begenerated.

Handovers in a case where the serving eNB is the macro eNB, for example,a handover from a macro eNB to another macro eNB or a handover from amacro eNB to a small eNB, and handovers in a case where the serving eNBis the small eNB, for example, a handover from a small eNB to a macroeNB or a handover from a small eNB to another small eNB may havedifferent characteristics. Further, handovers in a case where the targeteNB is the macro eNB, for example, a handover from a macro eNB toanother macro eNB or a handover from a small eNB to a macro eNB, andhandovers in a case where the target eNB is the small eNB, for example,a handover from a macro eNB to a small eNB or a handover from a smalleNB to another small eNB may also have different characteristics.

A handover performed when the serving eNB is the macro eNB,particularly, a handover from a macro eNB to a small eNB is generatedwhen a channel gain between the UE and the serving eNB is high. Ahandover performed when the serving eNB is the small eNB is generatedwhen the channel gain is always low.

That is, when the serving eNB is the macro eNB, the small eNB is locatedwithin a communication area of the macro eNB. Accordingly, a handoverfrom the macro eNB to the small eNB is not generated in an edge part ofthe communication area of the macro eNB, and accordingly is generatedwhen the channel gain is relatively high. However, when the serving eNBis the small eNB, both a handover from a small eNB to another small eNBand a handover from a small eNB to a macro eNB are generated in an edgepart of the communication area of the small eNB, and thus are generatedwhen the channel gain is relatively low.

Further, the macro eNB has a wide and continuous communication area, andaccordingly, the communication area of the macro eNB may accept all UEsmoving at fast speeds and stopping UEs regardless of mobility of theUEs. In contrast, the small eNB has a narrow and discontinuouscommunication area, and, accordingly, the communication area of thesmall eNB mainly accepts UEs moving at slow speeds.

However, when the UE moving at a fast speed performs a handover to asmall eNB, the UE should perform a handover again to another small eNBor a macro eNB in a short time due to the narrow and discontinuouscommunication area of the small eNB. Accordingly, even though there is asmall eNB near the UE moving at a fast speed, it may be better not toperform the handover to the small eNB in some cases. While the movementspeed of the UE in the handover does not need to be considered when thetarget eNB is the macro eNB, the movement speed of the UE acts as animportant parameter which should be considered in the handover when thetarget eNB is the small eNB.

Hereinafter, when the UE performs a handover, a method of applyingdifferent handover parameters, that is, different TTTs according to atype of a serving eNB, a type of a target eNB, and a combination of aserving eNB and a target eNB will be described in more detail.

The UE is required to distinguish between types of eNBs, for example,cell types to apply different TTTs according to an eNB type or an eNBcombination. Hereinafter, the eNB type and the cell type will be used asthe same meaning

There are two methods in which the UE distinguishes between cell types.In the first method, when the eNB broadcasts its own system information,the eNB explicitly transmits information on its own cell type. In thesecond method, when a system manager allocates physical cell Identifiers(IDs) to eNBs, the system manager allocates different cell IDs accordingto an eNB type.

Table 1 shows a correlation between an eNB type and a physical cell ID.

TABLE 1 eNB type Physical cell ID range Default [X0, X0 + Y0] Type 1[X1, X1 + Y1] Type 2 [X2, X2 + Y2] . . . . . . Type k [Xk, Xk + Yk] . .. . . .

When information shown in Table 1 is shared by the eNB, the systemmanager, and the UE, the UE may grasp information on an eNB type of aparticular eNB. For reference, [Xi, Xi+Yi] and [Xj, Xj+Yj] should be setso as not to overlap each other, and eNB types Type 1, Type 2, and Type3 may be a micro eNB, a pico eNB, and a femto eNB, respectively. Theexpression format [Xi, Xi+Yi] corresponds to a set of physical cell IDsincluded in a range from a physical cell ID Xi to a physical cell IDXi+Yi. Further, an eNB type default may include a macro eNB or an eNBwhich does not need to be classified specifically.

According to an embodiment of the present disclosure, when each eNBprovides information on eNBs adjacent to the eNB itself, the format asshown in Table 2 is used. Such a format is referred to as, for example,a cell type list.

TABLE 2 SEQUENCE{{Cell ID X1, Y1}, {Cell ID X2, Y2}, ..., {Cell ID Xk,Yk}, ...}

In the sequence shown in Table 2, a set of physical cell IDs included inkth round brackets corresponds to a kth eNB type. That is, the kth roundbrackets mean that an eNB corresponding to a physical cell ID [Xk,Xk+Yk] is included in an eNB type k. When the cell type list isconfigured using an index k indicating a kth eNB type and then is sharedbetween the eNB and the UE, the UE may identify physical cell IDs ofadjacent eNBs and recognize the eNB types of corresponding eNBs.

Next, each eNB provides a parameter considered when the handover eventis detected, that is, TTT information to the UE. According to anembodiment of the present disclosure, the eNB provides the TTTinformation to the UE according to each eNB type or each individual eNB.First, when the TTT information is provided according to each eNB type,the eNB may use the following two methods. In the first method, the eNBinforms the UE of the TTT and then provides a scaling factor which isapplied according to each eNB type to the UE. In the second method, theeNB directly provides the TTT which is applied according to each eNBtype to the UE.

Table 3 shows a format for expressing a TTT SF per cell type list withwhich the eNB provides the UE.

TABLE 3 SEQUENCE (SIZE(1..maxCellType)) OF SpeedStateScaleFactorSpeedStateScaleFactors information element -- ASN1START -- ASN1STARTSpeedStateScaleFactors ::= SEQUENCE { sf-Medium ENUMERATED {oDot25,oDot5, oDot75, lDot0}, ※ Values larger than 1 such as 2Dot0 and 3Dot5can be applied sf-High ENUMERATED {oDot25, oDot5, oDot75, lDot0} ※Values larger than 1 such as 2Dot0 and 3Dot5 can be applied } --ASN1STOP

Table 4 shows a format for expressing a TTT per cell type list withwhich the eNB directly provides the UE.

TABLE 4 SEQUENCE (SIZE(1..maxCellType)) OF TimeToTrigger TimeToTriggerinformation element -- ASN1START TimeToTrigger ::= ENUMERATED {ms0,ms40, ms64, ms80, ms100, ms128, ms160, ms256, ms320, ms480, ms512,ms640, ms1024, ms1280, ms2560, ms5120} ※ The specified values correspondto examples, and larger values may be applied -- ASN1STOP

As shown in Tables 3 and 4, in the TTT SF per cell type list, SEQUENCE(SIZE(1..maxCellType)) OF SpeedStateScaleFactor is expressed. In the TTTper cell type list, SEQUENCE (SIZE(1..maxCellType)) OF TimeToTrigger isexpressed.

That is, the cell type list corresponds to the sequence ofSpeedStateScaleFactor defined in 3rd Generation Partnership Project(3GPP) release-11 in the method of providing the TTT SF per cell typelist, and the cell type list corresponds to the sequence ofTimeToTrigger defined in 3GPP release-11 in the method of providing theTTT per cell type list. Further, maxCellType shown in Tables 3 and 4refers to the number of types of eNBs defined by the system manager, andthe number of types of eNBs is the same as the number of items includedin the cell type list (that is, the number of round brackets in thesequence).

For reference, the present disclosure is not limited to the scalingfactors or TTTs listed in Table 3 and 4, which are only examples, anddifferent values can be used.

When the eNB provides information on the TTT to the UE according to eacheNB type, the cell type list index k and TTT information, that is, theindex k of the TTT SF per cell type list shown in Table 3 and the indexof the TTT per cell type list shown in Table 4 refer to the same eNBtype. In this case, when the UE receives the TTT SF per cell type listshown in Table 3 from the eNB, the UE applies a default TTT*SFk to aneNB included in a kth eNB type. When the UE receives the TTT per celltype list from the eNB, the UE applies a TTTk to an eNB included in akth eNB type. When the TTT information is provided according to eachindividual eNB, the UE can directly grasp a scaling factor or a TTTapplied to each eNB, so that a separate analysis process is notrequired.

When the TTT information is provided according to each individual eNB,the eNB may use the following two methods. In the first method, the eNBinforms the UE of a default TTT and then provides a scaling factor whichis applied according to each individual eNB to the UE. In the secondmethod, the eNB directly provides the TTT which is applied according toeach individual eNB to the UE.

Table 5 shows a format for expressing a TTT SF per cell in which the TTTSF is provided according to each individual eNB, not each cell type.

TABLE 5 timeToTrigger SpeedStateScaleFactors SpeedStateScaleFactorsinformation element -- ASN1START SpeedStateScaleFactors ::= SEQUENCE {sf-Medium ENUMERATED {oDot25, oDot5, oDot75, lDot0}, ※ Values largerthan 1 such as 2Dot0 and 3Dot5 can be applied sf-High ENUMERATED{oDot25, oDot5, oDot75, lDot0} ※ Values larger than 1 such as 2Dot0 and3Dot5 can be applied } -- ASN1STOP

Table 6 shows a format for expressing a TTT per cell in which the TTT isprovided according to each individual eNB, not each cell type.

TABLE 6 timeToTrigger TimeToTrigger TimeToTrigger information element --ASN1START TimeToTrigger ::= ENUMERATED {ms0, ms40, ms64, ms80, ms100,ms128, ms160, ms256, ms320, ms480, ms512, ms640, ms1024, ms1280, ms2560,ms5120} ※ The specified values correspond to examples, and larger valuesmay be applied -- ASN1STOP

As shown in Tables 6 and 7, when the eNB provides the TTT SF per cell orthe TTT per cell to the UE, the corresponding information is irrelevantto the cell type, so that a very simple expression is possible. In thiscase, since a cell index (cellIndex) and a physical cell ID (physCellId)are included in a message including a TTT scaling factor or a TTT asshown in Table 7, the UE can easily grasp the TTT scaling factor or theTTT. Although not shown in Table 7, the TTT SF per cell or the TTT percell may be included in a System Information Block type 3 (SIB3). Inthis case, the UE may receive SIB3 and identify a TTT scaling factor ora TTT which can be applied to the eNB having transmitted SIB3.

Table 7 shows an example in which information on a TTT SF per call or aTTT per cell is included in CellsToAddMod of MEASOBJECTEUTRA IE.

TABLE 7 CellsToAddMod ::= SEQUENCE { cellIndex INTEGER (1..maxCellMeas),physCellId cellIndividualOffset Q-OffsetRange timeToTriggerSpeedStateScaleFactors OPTIONAL --Need ON (or timeToTriggerTimeToTrigger OPTIONAL --Need ON) }

According to information shown in Table 7, the UE applies differentscaling factors based on its own mobility state as well as an eNB type.For example, the mobility state of the UE is determined based on thenumber of handovers or cell (re)selections for a predetermined time.

FIG. 8 shows a format for expressing mobility state parameters per celltype to set different mobility related parameters according to an eNBtype.

TABLE 8 SEQUENCE (SIZE(1..maxCellType)) OF MobilityStateParametersMobilityStateParameters information element -- ASN1STARTMobilityStateParameters ::= SEQUENCE { t-Evaluation ENUMERATED {s30,s60, s120, s180, s240, spare3, spare2, spare1}, t-HystNormal ENUMERATED{s30, s60, s120, s180, s240, spare3, spare2, spare1}, n-CellChangeMediumINTEGER (1..16), n-CellChangeHigh INTEGER (1..16) } -- ASN1STOP

As shown in Table 8, the mobility state parameters per cell type areexpressed as SEQUENCE (SIZE(1..maxCellType)) OF MobilityStateParameters.That is, it means a sequence of MobilityStateParameters defined in 3GPPRel-11. For reference, the present disclosure is not limited tot-Evaluation, t-HystNormal, n-CellChangeMedium, and n-CellChangeHighlisted in Table 8, which are only examples, and different values can beapplied.

When information required for determining UE mobility is providedaccording to each eNB type, an index k of the cell type list and anindex k of the mobility state parameters per cell type refer to the sameeNB type. The UE mobility is determined by using mobility stateparameter information included in a kth sequence for an eNB included ina kth eNB type.

FIG. 5 illustrates an example flow diagram in which an eNB provides ahandover parameter to a UE in a mobile communication system according toan embodiment of the present disclosure.

Referring to FIG. 5, an eNB 500 transmits cell type information, TTTinformation, and mobility information to a UE 510 in operation 520. Thecell type information includes the cell type list shown in Table 2, theTTT information includes the TTT SF per cell type list and the TTT percell type list shown in Table 3 and 4, and the mobility informationincludes the mobility state parameters per cell type shown in Table 8.Each piece of information is included in messages shown in Tables 9 and10.

Table 9 shows an example of a message including handover parameterswhich the eNB provides to the UE.

TABLE 9 Message Main content and role of message MeasConfig The IEMeasConfig specifies measurements to be performed by the UE, and coversintra- frequency, inter-frequency and inter-RAT mobility as well asconfiguration of measure- ment gaps. MeasObjectEUTRA The IEMeasObjectEUTRA specifies information applicable for intra-frequency orinter- frequency E UTRA cells. ReportConfigEUTRA The IEReportConfigEUTRA specifies criteria for triggering of an E UTRAmeasurement reporting event. SIB3 Cell reselection parameters forintra-frequency, inter-frequency and inter-RAT. SIB3 contains cellre-selection information common for intra- frequency, inter-frequencyand inter-RAT cell reselection.

Table 10 shows an inclusion relationship between each piece ofinformation, that is, the cell type information, the TTT information,and the mobility information, and each of the messages shown in Table 9.

TABLE 10 MeasConfig MeasObjectEUTRA ReportConfigEUTRA SIB3 Cell type ◯ ◯◯ ◯ TTT Per cell type Scaling factor ◯ ◯ ◯ ◯ Absolute ◯ ◯ ◯ ◯ Per cellScaling factor X ◯ X ◯ Absolute X ◯ X ◯ Mobility state parameters ◯ ◯ ◯◯

Each piece of information shown in Table 10 and messages including theinformation will be described below.

Cell Type in MeasConfig Information Element (IE)

The cell type is defined as a range of only physical cell IDs. The celltype list may be defined as a sequence of cell types, and accordingly,may include one or more ranges of physical cell IDs which can beanalyzed in every index of the corresponding sequence. For example, whenthe cell type list is defined as SEQUENCE {{CellID1, 10}, {CellID50,20}}, cells having cell IDs from 1 to 10 are cell type 1, and cellshaving cell IDs from 50 to 70 are cell type 2. Cells having cell IDswhich are not included in any cell ID ranges listed in cell types may beincluded in a default cell type. For example, one or more cellscorresponding to the default cell type may be a macro cell. Further, oneor more cells corresponding to cell type 2 may be a pico cell, and oneor more cells corresponding to cell type 1 may be a femto cell.

The cell type list may be added to “MeasConfig IE” which can be includedin a Radio Resource Control (RRC) reconfiguration message. WhenMeasConfig IE including the cell type list is received, the UE realizesthe cell type which should be measured.

Cell Type in MeasObjectEUTRA IE

The cell type list may be added to “MeasObjectEUTRA IE” which can beincluded in an RRC reconfiguration message. When MeasObjectEUTRA IEincluding the cell type list is received, the UE realizes the cell typewhich should be measured.

Cell Type in ReportConfigEUTRA IE

The cell type list may be added to “ReportConfigEUTRA IE” which can beincluded in an RRC reconfiguration message. When ReportConfigEUTRA IEincluding the cell type list is received, the UE realizes the cell typewhich should be measured.

The cell type list may be added to a system information message. Forexample, the cell type list may be included in SIB3. When SIB3 includingthe cell type list is received, the UE may know the types of cellsexisting in the system. When a measurement configuration messageincluding the cell type list is received, the UE measures only cellscorresponding to the cell types. Otherwise, the UE measures cellscorresponding to all cell types as defined in SIB3.

Alternatively, when the cell type list is included in SIB3, themeasurement configuration message (MeasConfig or MeasObjectEUTRA IE) mayinclude only indexes of cell types which should be measured (cell typesaccording to CellTypeList defined in SIB3). The definition maycorrespond to CellTypesToMeasure::=SEQUENCE {INTEGER (1 . . . ,maxCellTypes}. The default cell type should be measured regardless ofthe measurement related message including the cell type list, but shouldnot be measured when the cell type list defines cell types which are notthe default cell type.

TTT (TTT Based on Scaling Factor) in ReportConfigEUTRA IE

The TTT is defined per cell type and defined as a TTT-related scalingfactor for the default cell type. TimeToTriggerPerCellType is defined asa sequence of the TTT. A TTT entry within the sequence is an entrywithin a sequence corresponding to a cell type corresponding to an indexwithin a cell type list sequence which is the same as an index of a TTTentry within a TimeToTriggerPerCellType sequence. According to anembodiment of the present disclosure, TimeToTriggerPerCellType may beincluded in ReportConfigEUTRA IE. When receiving ReportConfigEUTRAincluding TimeToTriggerPerCellType, the UE may know a cell type and aTTT which should be used for the cell type.

TTT (Absolute TTT) in ReportConfigEUTRA IE

The TTT is defined per cell type, and defined as an absolute value.TimeToTriggerPerCellType is defined as the sequence of TTT. A TTT entrywithin the sequence is an entry within a sequence corresponding to acell type corresponding to an index within a cell type list sequencewhich is the same as an index of a TTT entry within aTimeToTriggerPerCellType sequence. According to an embodiment of thepresent disclosure, TimeToTriggerPerCellType may be included inReportConfigEUTRA IE. When receiving ReportConfigEUTRA includingTimeToTriggerPerCellType, the UE may know a cell type and a TTT whichshould be used for the cell type.

TTT (TTT Based on Scaling Factor) in MeasConfig IE

TimeToTriggerPerCellType including the sequence of TTTs defined as thescaling factors related to the TTT for the default cell type may beincluded in MeasConfig IE. When receiving MeasConfig IE includingTimeToTriggerPerCellType, the UE may know a cell type and a TTT whichshould be used for the cell type.

TTT (Absolute TTT) in MeasConfig IE

TimeToTriggerPerCellType including the sequence of TTTs defined asabsolute values for cell types may be included in MeasConfig IE. Whenreceiving MeasConfig IE including TimeToTriggerPerCellType, the UE mayknow a cell type and a TTT which should be used for the cell type.

TTT (TTT Based on Scaling Factor per Cell Type) in MeasObjectEUTRA IE

TimeToTriggerPerCellType including the sequence of TTTs defined as thescaling factors related to the TTT for the default cell type may beincluded in MeasObjectEUTRA IE. When receiving MeasObjectEUTRA IEincluding TimeToTriggerPerCellType, the UE may know a cell type and aTTT which should be used for the cell type.

TTT (Absolute TTT per Cell Type) in MeasObjectEUTRA IE

TimeToTriggerPerCellType including the sequence of TTTs defined asabsolute values for cell types may be included in MeasObjectEUTRA IE.When receiving MeasObjectEUTRA IE including TimeToTriggerPerCellType,the UE may know a cell type and a TTT which should be used for the celltype.

TTT (Absolute TTT per Cell) in MeasObjectEUTRA IE

The TTT may be individually defined in an absolute way per cell, and maybe included in MeasObjectEUTRA IE. When receiving MeasObjectEUTRA IEincluding TimeToTriggerPerCellType, the UE may know a cell type whichshould be measured and a TTT which should be used for the cell type.

TTT (TTT Based on Scaling Factor per Cell) in MeasObjectEUTRA IE

The TTT may be individually defined in a scaling factor way per cell,and may be included in MeasObjectEUTRA IE. When receivingMeasObjectEUTRA IE including TimeToTriggerPerCellType, the UE may know acell type which should be measured and a TTT which should be used forthe cell type.

TTT (TTT Based on Scaling Factor) in SIB3

TimeToTriggerPerCellType including the sequence of TTTs defined as thescaling factors related to the TTT for the default cell type may beincluded in the system information message such as SIB3. When receivingSIB3 including TimeToTriggerPerCellType, the UE may know a cell type anda TTT which should be used for the cell type.

Trigger Time in SIB3 (Absolute TTT)

TimeToTriggerPerCellType including the sequence of TTTs defined asabsolute values for cell types may be included in MeasConfig IE. Whenreceiving MeasConfig IE including TimeToTriggerPerCellType, the UE mayknow a cell type and a TTT which should be used for the cell type.

Mobility State Parameters (MobilityStateParameter) per Cell Type WithinSIB3

The mobility state parameters are defined per cell type.MobilityStateParametersPerCellType is defined as a sequence of the TTT.A TTT entry within the sequence is an entry within a sequencecorresponding to a cell type corresponding to an index within a celltype list sequence which is the same as an index of an entry of mobilitystate parameters within a MobilityStateParametersPerCellType sequence.According to an embodiment, MobilityStateParametersPerCellType may beincluded in system information messages such as SIB3. When receivingSIB3 including MobilityStateParametersPerCellType, the UE may know acell type and mobility state parameters which should be used for thecell type.

Mobility State Parameters per Cell Type within MeasConfig IE

MobilityStateParametersPerCellType may be included in MeasConfig IE.When receiving MeasConfig IE includingMobilityStateParametersPerCellType, the UE may know a cell type andmobility state parameters which should be used for the cell type.

Mobility State Parameters per Cell Type within MeasObjectEUTRA IE

MobilityStateParametersPerCellType may be included in MeasObjectEUTRAIE. When receiving MeasObjectEUTRA IE includingMobilityStateParametersPerCellType, the UE may know a cell type andMobilityStateParameters which should be used for the cell type.

Mobility State Parameters per Cell Type Within ReportConfigEUTRA IE

MobilityStateParametersPerCellType may be included in ReportConfigEUTRAIE. When receiving ReportConfigEUTRA IE includingMobilityStateParametersPerCellType, the UE may know a cell type andMobilityStateParameters which should be used for the cell type.

Format for Expressing Cell Types in MeasConfig IE

TABLE 11 -- ASN1START MeasConfig ::= SEQUENCE { -- Measurement objectsmeasObjectToRemoveList MeasObjectToRemoveList OPTIONAL, -- Need ONmeasObjectToAddModList MeasObjectToAddModList OPTIONAL, -- Need ON --Reporting configurations reportConfigToRemoveListReportConfigToRemoveList OPTIONAL, -- Need ON reportConfigToAddModListReportConfigToAddModList OPTIONAL, -- Need ON -- Measurement identitiesmeasIdToRemoveList MeasIdToRemoveList OPTIONAL, -- Need ONmeasIdToAddModList MeasIdToAddModList OPTIONAL, -- Need ON -- Otherparameters ... (omit) } cellTypeList CellTypeList OPTIONAL -- Need ONCellTypeList ::= SEQUENCE (SIZE (1..maxCellType)) OF CellTypes CellTypes::= SEQUENCE { phyCellIdRange PhyCellIdRange } ... (omit) -- ASN1STOP

Format for Expressing Cell Types in MeasObjectEUTRA IE

TABLE 12 -- ASN1START MeasObjectEUTRA ::= SEQUENCE { carrierFreqARFCN-ValueEUTRA, ... (omit) cellTypeList CellTypeList OPTIONAL -- NeedON } ... (omit) CellsToAddMod ::= SEQUENCE { cellIndex INTEGER(1..maxCellMeas), physCellId PhysCellId, cellIndividualOffsetQ-OffsetRange } ... (omit) CellTypeList ::= SEQUENCE (SIZE(1..maxCellType)) OF CellTypes CellTypes ::= SEQUENCE {phyCellIdRangePhyCellIdRange } -- ASN1STOP

Format for Expressing Cell Types in ReportConfigEUTRA IE

TABLE 13 -- ASN1START ReportConfigEUTRA ::= SEQUENCE { triggerTypeCHOICE { event SEQUENCE { eventId CHOICE { eventA1SEQUENCE {a1-Threshold ThresholdEUTRA }, ... (omit) }, triggerQuantity ENUMERATED{rsrp, rsrq}, ... (omit) cellTypeList CellTypeList OPTIONAL -- Need ON }ThresholdEUTRA ::= CHOICE{ threshold-RSRP RSRP-Range, threshold-RSRQRSRQ-Range } CellTypeList ::= SEQUENCE (SIZE (1..maxCellType)) OFCellTypes CellTypes::= SEQUENCE { phyCellIdRange PhyCellIdRange } --ASN1STOP

Format for Expressing Cell Types in SIB3

TABLE 14 -- ASN1START SystemInformationBlockType3 ::= SEQUENCE {cellReselectionInfoCommon SEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2,dB3, dB4, dB5, dB6, dB8, dB10, dB12, dB14, dB16, dB18, dB20, dB22,dB24}, speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6,dB-4, dB-2, dB0}, sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP cellTypeList CellTypeList OPTIONAL -- Need ON }, ...(omit) CellTypeList ::= SEQUENCE (SIZE (1..maxCellType)) OF CellTypesCellTypes::= SEQUENCE { phyCellIdRange PhyCellIdRange } } -- ASN1STOP

Format for Expressing TTT (TTT Based on Scaling Factor) inReportConfigEUTRA IE

TABLE 15 -- ASN1START ReportConfigEUTRA ::= SEQUENCE { triggerTypeCHOICE { event SEQUENCE { eventId CHOICE { eventA1 SEQUENCE {a1-Threshold ThresholdEUTRA }, eventA2 SEQUENCE { a2-ThresholdThresholdEUTRA }, eventA3 SEQUENCE { a3-Offset INTEGER (−30..30),reportOnLeave BOOLEAN }, eventA4 SEQUENCE { a4-Threshold ThresholdEUTRA}, eventA5 SEQUENCE { a5-Threshold1 ThresholdEUTRA, a5-Threshold2ThresholdEUTRA }, ..., eventA6-r10 SEQUENCE { a6-Offset-r10 INTEGER(−30..30), a6-ReportOnLeave-r10 BOOLEAN } }, hysteresis Hysteresis,timeToTrigger TimeToTrigger timeToTriggerPerCellTypeTimeToTriggerPerCellType OPTIONAl --Need ON }, periodical SEQUENCE {purpose ENUMERATED { reportStrongestCells, reportCGI} } }, ... (omit)TimeToTriggerPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes)) OFSpeedStateScaleFactors -- ASN1STOP

Format for Expressing TTT (Absolute TTT) in ReportConfigEUTRAIE

TABLE 16 -- ASN1START ReportConfigEUTRA ::=SEQUENCE { triggerType CHOICE{ event SEQUENCE { eventId CHOICE { eventA1SEQUENCE { a1-ThresholdThresholdEUTRA }, eventA2 SEQUENCE { a2-Threshold ThresholdEUTRA },eventA3 SEQUENCE { a3-Offset INTEGER (−30..30), reportOnLeave BOOLEAN },eventA4 SEQUENCE { a4-Threshold ThresholdEUTRA }, eventA5 SEQUENCE {a5-Threshold1 ThresholdEUTRA, a5-Threshold2 ThresholdEUTRA }, ...,eventA6-r10 SEQUENCE { a6-Offset-r10 INTEGER (−30..30),a6-ReportOnLeave-r10 BOOLEAN } }, hysteresis Hysteresis, timeToTriggerTimeToTrigger timeToTriggerPerCellType TimeToTriggerPerCellType OPTIONAl--Need ON }, Periodical SEQUENCE { purpose ENUMERATED {reportStrongestCells, reportCGI} } }, ... (omit)TimeToTriggerPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes)) OFTimeToTrigger -- ASN1STOP

Format for Expressing TTT (TTT Based on Scaling Factor) in MeasConfig IE

TABLE 17 -- ASN1START MeasConfig ::= SEQUENCE { -- Measurement objectsmeasObjectToRemoveList MeasObjectToRemoveList OPTIONAL, -- Need ONmeasObjectToAddModList MeasObjectToAddModList OPTIONAL, -- Need ON --Reporting configurations reportConfigToRemoveListReportConfigToRemoveList OPTIONAL, -- Need ON reportConfigToAddModListReportConfigToAddModList OPTIONAL, -- Need ON -- Measurement identitiesmeasIdToRemoveList MeasIdToRemoveList OPTIONAL, -- Need ONmeasIdToAddModList MeasIdToAddModList OPTIONAL, -- Need ON -- Otherparameters quantityConfig QuantityConfig OPTIONAL, -- Need ON ... (omit)} timeToTriggerPerCellType TimeToTriggerPerCellType OPTIONAl --Need ONTimeToTriggerPerCellType ::= SEQUENCE(SIZE (1..maxCellTypes)) OFSpeedStateScaleFactors ... (omit) -- ASN1STOP

Format for Expressing TTT (Absolute TTT) in MeasConfig IE

TABLE 18 -- ASN1START MeasConfig ::= SEQUENCE { -- Measurement objectsmeasObjectToRemoveList MeasObjectToRemoveList OPTIONAL, -- Need ONmeasObjectToAddModList MeasObjectToAddModList OPTIONAL, -- Need ON --Reporting configurations reportConfigToRemoveListReportConfigToRemoveList OPTIONAL, -- Need ON reportConfigToAddModListReportConfigToAddModList OPTIONAL, -- Need ON -- Measurement identitiesmeasIdToRemoveList MeasIdToRemoveList OPTIONAL, -- Need ONmeasIdToAddModList MeasIdToAddModList OPTIONAL, -- Need ON -- Otherparameters quantityConfig QuantityConfig OPTIONAL, -- Need ON ... (omit)} timeToTriggerPerCellType TimeToTriggerPerCellType OPTIONAl --Need ONTimeToTriggerPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes)) OFTimeToTrigger ... (omit) -- ASN1STOP

Format for Expressing TTT (TTT Based on Scaling Factor per Cell Type) inMeasObjectEUTRA IE

TABLE 19 -- ASN1START MeasObjectEUTRA ::= SEQUENCE { carrierFreqARFCN-ValueEUTRA, ... (omit) timeToTriggerPerCellTypeTimeToTriggerPerCellType OPTIONAl --Need ON } ... (omit)TimeToTriggerPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes)) OFSpeedStateScaleFactors -- ASN1STOP

Format for Expressing TTT (Absolute TTT per Cell Type) inMeasObjectEUTRA IE

TABLE 20 -- ASN1START MeasObjectEUTRA ::= SEQUENCE { carrierFreqARFCN-ValueEUTRA, ... (omit) timeToTriggerPerCellTypeTimeToTriggerPerCellType OPTIONAl --Need ON } ... (omit)TimeToTriggerPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes)) OFTimeToTrigger -- ASN1STOP

Format for Expressing TTT (Absolute TTT per Cell) in MeasObjectEUTRA IE

TABLE 21 -- ASN1START MeasObjectEUTRA ::= SEQUENCE { carrierFreqARFCN-ValueEUTRA, allowedMeasBandwidth AllowedMeasBandwidth,presenceAntennaPort1 PresenceAntennaPort1, neighCellConfigNeighCellConfig, offsetFreq Q-OffsetRange DEFAULT dB0, -- Cell listcellsToRemoveList CellIndexList OPTIONAL, -- Need ON cellsToAddModListCellsToAddModList OPTIONAL, -- Need ON ... (omit) } CellsToAddModList::= SEQUENCE (SIZE (1..maxCellMeas)) OF CellsToAddMod CellsToAddMod ::=SEQUENCE { cellIndex INTEGER (1..maxCellMeas), physCellId PhysCellId,cellIndividualOffset Q-OffsetRange timeToTrigger TimeToTrigger OPTIONAl--Need ON } ... (omit) -- ASN1STOP

Format for Expressing TTT (TTT Based on Scaling Factor per Cell) inMeasObjectEUTRA IE

TABLE 22 -- ASN1START MeasObjectEUTRA ::= SEQUENCE { carrierFreqARFCN-ValueEUTRA, allowedMeasBandwidth AllowedMeasBandwidth,presenceAntennaPort1 PresenceAntennaPort1, neighCellConfigNeighCellConfig, offsetFreq Q-OffsetRange DEFAULT dB0, -- Cell listcellsToRemoveList CellIndexList OPTIONAL, -- Need ON cellsToAddModListCellsToAddModList OPTIONAL, -- Need ON ... (omit) } CellsToAddModList::= SEQUENCE (SIZE (1..maxCellMeas)) OF CellsToAddMod CellsToAddMod ::=SEQUENCE { cellIndex INTEGER (1..maxCellMeas), physCellId PhysCellId,cellIndividualOffset Q-OffsetRange timeToTrigger SpeedStateScaleFactorsOPTIONAl --Need ON } ... (omit) -- ASN1STOP

Format for Expressing TTT (TTT Based on Scaling Factor per Cell Type) inSIB3

TABLE 23 -- ASN1START SystemInformationBlockType3 ::= SEQUENCE {cellReselectionInfoCommon SEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2,dB3, dB4, dB5, dB6, dB8, dB10, dB12, dB14, dB16, dB18, dB20, dB22,dB24}, speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6,dB-4, dB-2, dB0}, sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP timeToTriggerPerCellType TimeToTriggerPerCellTypeOPTIONAL --Need ON }, ... (omit) TimeToTriggerPerCellType ::= SEQUENCE(SIZE (1..maxCellTypes)) OF SpeedStateScaleFactors } -- ASN1STOP

Format for Expressing TTT (Absolute TTT per Cell Type) in SIB3

TABLE 24 -- ASN1START SystemInformationBlockType3 ::= SEQUENCE {cellReselectionInfoCommon SEQUENCE { q-Hyst ENUMERATED { dB0, dB1, dB2,dB3, dB4, dB5, dB6, dB8, dB10, dB12, dB14, dB16, dB18, dB20, dB22,dB24}, speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6,dB-4, dB-2, dB0}, sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP timeToTriggerPerCellType TimeToTriggerPerCellTypeOPTIONAl --Need ON }, ... (omit) TimeToTriggerPerCellType ::= SEQUENCE(SIZE (1..maxCellTypes)) OF TimeToTrigger } -- ASN1STOP

Format for Expressing Mobility State Parameters (MobilityStateParameter)per Cell Type Within SIB3

TABLE 25 -- ASN1START SystemInformationBlockType3 ::= SEQUENCE {cellReselectionInfoCommon SEQUENCE { q-Hyst ENUMERATED {dB0, dB1, dB2,dB3, dB4, dB5, dB6, dB8, dB10, dB12, dB14, dB16, dB18, dB20, dB22,dB24}, speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6,dB-4, dB-2, dB0}, sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP mobilityStateParametersPerCellTypeMobilityStateParametersPerCellTypeOPTIONAl --Need ON }, ... (omit)MobilityStateParametersPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes))OF MobilityStateParameters } -- ASN1STOP

Format for Expressing Mobility State Parameters per Cell Type WithinMeasConfig IE

TABLE 26 -- ASN1START MeasConfig ::= SEQUENCE { -- Measurement objectsmeasObjectToRemoveList MeasObjectToRemoveList OPTIONAL, -- Need ONmeasObjectToAddModList MeasObjectToAddModList OPTIONAL, -- Need ON --Reporting configurations reportConfigToRemoveListReportConfigToRemoveList OPTIONAL, -- Need ON reportConfigToAddModListReportConfigToAddModList OPTIONAL, -- Need ON -- Measurement identitiesmeasIdToRemoveList MeasIdToRemoveList OPTIONAL, -- Need ONmeasIdToAddModList MeasIdToAddModList OPTIONAL, -- Need ON -- Otherparameters quantityConfig QuantityConfig OPTIONAL, -- Need ON ... (omit)} mobilityStateParametersPerCellTypeMobilityStateParametersPerCellTypeOPTIONAl -- Need ONMobilityStateParametersPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes))OF MobilityStateParameters ... (omit) -- ASN1STOP

Format for Expressing Mobility State Parameters per Cell Type WithinMeasObjectEUTRA IE

TABLE 27 -- ASN1START MeasObjectEUTRA ::= SEQUENCE { carrierFreqARFCN-ValueEUTRA, ... (omit) mobilityStateParametersPerCellTypeMobilityStateParametersPerCellType OPTIONAl --Need ON } ... (omit)MobilityStateParametersPerCellType ::= SEQUENCE (SIZE (1..maxCellTypes))OF MobilityStateParameters -- ASN1STOPFormat for Expressing Mobility State Parameters per Cell Type withinReportConfigEUTRA IE

TABLE 28 -- ASN1START ReportConfigEUTRA ::= SEQUENCE { triggerTypeCHOICE { event SEQUENCE { eventId CHOICE { eventA1 SEQUENCE {a1-Threshold ThresholdEUTRA }, eventA2 SEQUENCE { a2-ThresholdThresholdEUTRA }, eventA3 SEQUENCE { a3-Offset INTEGER (−30..30),reportOnLeave BOOLEAN }, eventA4 SEQUENCE { a4-Threshold ThresholdEUTRA}, eventA5SEQUENCE { a5-Threshold1 ThresholdEUTRA, a5-Threshold2ThresholdEUTRA }, ..., eventA6-r10 SEQUENCE { a6-Offset-r10 INTEGER(−30..30), a6-ReportOnLeave-r10 BOOLEAN } }, hysteresis Hysteresis,timeToTrigger TimeToTrigger mobilityStateParametersPerCellTypeMobilityStateParametersPerCellType OPTIONAL --Need ON }, ... (omit) }... (omit) MobilityStateParametersPerCellType ::= SEQUENCE (SIZE(1..maxCellTypes)) OF MobilityStateParameters -- ASN1STOP

Format for Expressing TTT (TTT Based on Scaling Factor per Cell) in SIB3

TABLE 29 -- ASN1START SystemInformationBlockType3 ::= SEQUENCE {cellReselectionInfoCommon SEQUENCE { q-Hyst ENUMERATED {dB0, dB1, dB2,dB3, dB4, dB5, dB6, dB8, dB10, dB12, dB14, dB16, dB18, dB20, dB22,dB24}, speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6,dB-4, dB-2, dB0}, sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP timeToTrigger SpeedStateScaleFactors OPTIONAl --NeedON }, ... (omit) } -- ASN1STOP

Format for Expressing TTT (Absolute TTT per Cell Type) in SIB3

TABLE 30 -- ASN1START SystemInformationBlockType3 ::= SEQUENCE {cellReselectionInfoCommon SEQUENCE { q-Hyst ENUMERATED {dB0, dB1, dB2,dB3, dB4, dB5, dB6, dB8, dB10, dB12, dB14, dB16, dB18, dB20, dB22,dB24}, speedStateReselectionPars SEQUENCE { mobilityStateParametersMobilityStateParameters, q-HystSF SEQUENCE { sf-Medium ENUMERATED {dB-6,dB-4, dB-2, dB0}, sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0} } }OPTIONAL -- Need OP timeToTrigger TimeToTrigger OPTIONAl --Need ON },... (omit) } -- ASN1STOP

The UE having received the above information from the serving eNB andthe target eNB should determine whether to set the TTT according to thetype of serving eNB or according to the type of target eNB. Thedetermination may be made by an implementation method of the UE or by acontrol method of the UE. For example, the UE may configure prioritiesof types of eNBs and provide the UE of information on the priorities,and the UE receiving the information may set the TTT according to theeNB type having a higher priority.

Last, when the source eNB is the macro eNB and the target eNB is thesmall eNB, the UE should determine whether to quickly perform a handoverto the small eNB by using a short TTT or not perform the handover to thecorresponding small eNB by using a long TTT. The UE may consider amovement speed of the UE when determining whether to use the short TTTor the long TTT. That is, when the movement speed is fast, a time forwhich the UE stays in the corresponding small eNB is short, and thus theUE avoids the handover by applying the long TTT. Further, in determiningwhether to use the short TTT or the long TTT, the UE may consider achannel gain between the UE and the source eNB as well as the movementspeed of the UE. The short TTT refers to a TTT having a value smallerthan a preset value (non-scaled default value) and the long TTT refersto a TTT having a value larger than or equal to the preset value(non-scaled default value).

When a channel gain between the UE and the source eNB is sufficient, theUE does not need to be handed over to the small eNB corresponding to thetarget eNB. This is because, in comparison between a capability gainacquired from the handover and a capability reduction due to overheadsgenerated by the handover (for example, interruption time or signalingoverheads), the capability gain from the handover is not larger. Incontrast, when the channel gain between the UE and the source eNB is notgood, it is preferable that the UE performs the handover to the smalleNB. In this case, even though the interruption time and signaloverheads are generated by the handover, service quality experienced bythe UE is more important. Accordingly, in various embodiments of thepresent disclosure described below, when the handover from the macro eNBto the small eNB is generated, the following operations are executed.

1. When a speed of the UE is larger than or equal to a particular valueand RSRP serving of the serving eNB is also larger than or equal to aparticular value, the UE avoids the handover to the small eNB by using along TTT.

2. When a speed of the UE is larger than or equal to a particular valueand RSRP serving of the serving eNB is smaller than a particular value,the UE rapidly performs the handover to the small eNB by using a shortTTT.

FIG. 6 is a flowchart illustrating an example in which the UE adaptivelysets a TTT according to an embodiment of the present disclosure.

Referring to FIG. 6, when the UE detects the generation of a handoverfrom a macro eNB to a small eNB in operation 600, the UE proceeds tooperation 610. The generation of the handover from the macro eNB to thesmall eNB is detected based on the cell type information shown in Tables1 and 2 described above.

The UE identifies whether a movement speed of the UE is larger than apreset first threshold in operation 610, and proceeds to operation 620when the movement speed of the UE is larger than the first threshold.Whether the movement speed of the UE is larger than the first thresholdis identified based on mobility state parameters per cell type shown inTable 8 described above. That is, when the number of handovers/cell(re)selections generated during t-Evaluation is larger than or equal ton-CellChangeMedium and smaller than n-CellChangeHigh, a mobility stateof the UE is medium corresponding to a low level. When the number ofhandovers/cell (re)selections is larger than or equal ton-CellChangeHigh, the mobility state of the UE is high corresponding toa high level. Mobility states of UEs which do not correspond to mediumand high are normal corresponding to an intermediate level. Based onsuch a method, the threshold for the movement speed of the UE may be setas a high mobility state or a medium mobility state. In addition to themethod, a method depending on the implementation of the UE, for example,a method using a GPS may be considered.

The UE identifies whether reference signal received power for servingeNB RSRPserving is larger than an already known second threshold inoperation 620. When RSRPserving is larger than the second threshold, theUE proceeds to operation 630 and sets a TTT considered when a handoverevent is detected as a long TTT. Further, when RSRPserving is not largerthan the second threshold, that is, RSRPserving is smaller than thesecond threshold, the UE proceeds to operation 640 and sets a TTTconsidered when the handover event is detected as a short TTT. Thesecond threshold is a value which the serving eNB notifies to the UE,and is inserted into a broadcasting message of the serving eNB and thentransmitted. Further, the long TTT and the short TTT are distinguishedby the TTT per cell type and the TTT SF per cell type shown in Tables 3and 4. That is, higher N TTTs are determined as long TTTs in availableTTTs arranged in an ascending order and higher N TTTs are determined asshort TTTs in available TTT arranged in a descending order.

FIGS. 7A and 7B illustrate examples in which the UE uses a short TTT anda long TTT in a mobile communication system according to variousembodiments of the present disclosure.

Referring to FIGS. 7A and 7B, it is assumed that the serving eNB is themacro eNB and the target eNB is the small eNB, and a movement speed ofthe UE is faster than a predetermined threshold speed (UE movementspeed>threshold speed).

Referring to FIG. 7A, when a difference between a received signalstrength RSRPmacro received from the serving eNB and a received signalstrength RSRPsmall received from the target eNB is larger than or equalto a preset offset (A3 offset), the UE identifies whether RSRPmacro islarger than an already known RSRP threshold. In this case, RSRPmacro issmaller than the RSRP threshold, so that the UE sets the TTT consideredwhen the handover event is detected, as a short TTT.

Referring to FIG. 7B, when a difference between a received signalstrength RSRPmacro received from the serving eNB and a received signalstrength RSRPsmall received from the target eNB is larger than or equalto a preset offset (A3 offset), the UE identifies whether RSRPmacro islarger than an already known RSRP threshold. In this case, RSRPmacro islarger than the RSRP threshold, so that the UE sets the TTT consideredwhen the handover event is detected, as a long TTT.

In an embodiment of the present disclosure described through FIGS. 6,7A, and 7B, when the generation of the handover is detected, that is,when the UE detects the handover event, the UE determines whether toapply the long TTT or the short TTT according to the received signalstrength of the macro eNB corresponding to the serving eNB. However,since a radio channel generally varies as time goes by and considers ahandover state by movement of the current UE, the signal strength of themacro eNB measured by the UE also varies as time goes by.

Accordingly, the signal strength of the macro eNB may be reduced whilemonitoring whether the offset A3 is maintained during the long TTT afterthe UE determines to apply the long TTT, and accordingly RSRPmacro maybe changed into a value equal to or smaller than the RSRP threshold. Inthis case, the UE should consider switching from the long TTT to theshort TTT.

Similarly, the signal strength of the macro eNB may increase whilemonitoring whether the offset A3 is maintained during the short TTTafter the UE determines to apply the short TTT, and accordinglyRSRPmacro may be changed into a value larger than the RSRP threshold. Inthis case, the UE should consider switching from the short TTT to thelong TTT.

FIG. 8 is a flowchart illustrating an example in which the UE switches apreset long TTT to a short TTT in a mobile communication systemaccording to an embodiment of the present disclosure.

Referring to FIG. 8, the UE having applied the long TTT in operation 800identifies whether the long TTT has expired in operation 810. When thelong TTT has expired based on a result of the identification, the UEtransmits a measurement report message for a handover in operation 850.When the long TTT has not expired, the UE identifies whether referencesignal received power for the serving eNB RSRPserving is smaller than analready known RSRP threshold in operation 820.

The UE proceeds to operation 810 when RSRPserving is not greater thanthe RSRP threshold, and proceeds to operation 830 to identify a TTTprogressed up to a current time within the long TTT, that is, aTTTrunning value when RSRPserving is greater than the RSRP threshold.The UE identifies whether the TTTrunning value is larger than the shortTTT in operation 840. When the TTTrunning value is larger than the shortTTT, the UE transmits a measurement report message to the serving eNB toinitiate the handover process in operation 850. When TTTrunning islarger than the short TTT, it means that the TTT has already expiredfrom the perspective of the short TTT.

However, when TTTrunning is not larger than the short TTT, the UEswitches the currently applied TTT to the short TTT in operation 860.When TTTrunning is not larger than the short TTT, it means that the TTThas not yet expired from a view point of the short TTT. Further, the UEmonitors whether the offset A3 (RSRPtarget-RSRPserving) is maintainedduring the left TTT from the viewpoint of the short TTT, that is, duringTTT-TTTrunning

FIG. 9 is a flowchart illustrating an example in which the UE switches apreset short TTT to a long TTT in a mobile communication systemaccording to an embodiment of the present disclosure.

Referring to FIG. 9, having applied the short TTT in operation 900, theUE identifies whether the short TTT has expired in operation 910. Whenthe short TTT has expired based on a result of the identification, theUE transmits a measurement report message for a handover, and switchesthe currently applied short TTT to the long TTT in operation 940. Whenthe short TTT has not expired, the UE identifies whether referencesignal received power for the serving eNB RSRPserving is larger than analready known RSRP threshold in operation 920.

The UE proceeds to operation 910 when RSRPserving is not larger than theRSRP threshold, and proceeds to operation 930 to identify a TTTprogressed up to a current time within the short TTT, that is, aTTTrunning value when RSRPserving is larger than the RSRP threshold. Inoperation 940, the UE switches the currently applied short TTT to thelong TTT. Further, the UE monitors whether the offset A3(RSRPtarget-RSRPserving) is maintained during the left TTT from theviewpoint of the long TTT, that is, during TTT-TTTrunning

FIGS. 10A and 10B illustrate examples in which the UE switches acurrently applied TTT in a mobile communication system according tovarious embodiments of the present disclosure.

Referring to FIGS. 10A and 10B, it is assumed that the serving eNB isthe macro eNB and the target eNB is the small eNB, and a movement speedof the UE is faster than a predetermined threshold speed (UE movementspeed>threshold speed).

Referring to FIG. 10A, when a difference between a received signalstrength received from the serving eNB RSRPmacro and a received signalstrength received from the target eNB RSRPsmall is larger than or equalto a predetermined offset (offset A3), the UE identifies whetherRSRPmacro is larger than an already known RSRP threshold. In this case,since RSRPmacro is larger than the RSRP threshold, the UE sets a TTTconsidered when a handover event is detected as a long TTT. However,when RSRPmacro becomes smaller than the RSRP threshold before the longTTT has expired, the UE identifies a TTT value progressed up to acurrent time within the long TTT, that is, TTTrunning Then, the UEcompares TTTrunning with the short TTT. When TTTrunning is smaller thanthe short TTT, the UE switches the currently applied long TTT to theshort TTT.

Further, time information T1, T2, and T3 illustrated in FIG. 10A aredescribed below.

T1: refers to a time point when the UE detects offset A3 and determinesto apply the long TTT

T2: refers to a time point when the UE switches the long TTT to theshort TTT since the signal strength RSRPmacro received from the macroeNB corresponding to the serving eNB becomes smaller than the RSRPthreshold

T3: refers to a time point when a handover is initiated by additionallyidentifying whether offset A3 is maintained during short TTT-TTTrunningat the time point T2 when the long TTT is switched to the short TTT.

Referring to FIG. 10B, when a difference between a received signalstrength received from the serving eNB RSRPmacro and a received signalstrength received from the target eNB RSRPsmall is larger than or equalto a predetermined offset (offset A3), the UE identifies whetherRSRPmacro is larger than an already known RSRP threshold. In this case,since RSRPmacro is not larger than the RSRP threshold, the UE sets a TTTconsidered when a handover event is detected as a short TTT. However,when RSRPmacro becomes larger than the RSRP threshold before the shortTTT has expired, the UE identifies a TTT value progressed up to acurrent time within the short TTT, that is, TTTrunning Then, the UEswitches the currently applied short TTT to the long TTT.

Further, time information T4, T5, and T6 illustrated in FIG. 10B aredescribed below.

T4: refers to a time point when the UE detects offset A3 and determinesto apply the short TTT.

T5: refers to a time point when the UE switches the short TTT to thelong TTT since the signal strength RSRPmacro received from the macro eNBcorresponding to the serving eNB becomes larger than the RSRP threshold.

T6: refers to a time point when a handover to the small eNB is notperformed by additionally identifying whether offset A3 is maintainedduring short TTT-TTTrunning at the time point T5 when the short TTT isswitched to the long TTT.

As described through FIGS. 9, 10A, and 10B, the UE may adaptively changethe currently applied short TTT and long TTT according to a condition,and may determine whether to rapidly perform a handover to a small eNBbased on the short TTT or not perform the handover to the small eNBbased on the long TTT through the adaptive change in the TTTs.

It will be appreciated that the method and an apparatus for setting ahandover parameter according to the present disclosure may beimplemented in the form of hardware, software, or a combination ofhardware and software. Any such software may be stored, for example, ina volatile or non-volatile storage device such as a Read-Only Memory(ROM), a memory such as a Random Access Memory (RAM), a memory chip, amemory device, or a memory Integrated Circuit (IC), or a recordableoptical or magnetic medium such as a Compact Disc (CD), a DigitalVersatile Disc (DVD), a magnetic disk, or a magnetic tape, regardless ofits ability to be erased or its ability to be re-recorded. Also, it willbe appreciated that a graphic screen updating method according to thepresent disclosure may be implemented by a computer or a portableterminal which includes a controller and a memory, in which the memorymay be an example of a storage medium that is readable by a machine thatis suitable for storing one or more programs that include instructionsfor implementing the various embodiments of the present disclosure.

Accordingly, the present disclosure includes a program for a codeimplementing the apparatus and method described in the appended claimsof the specification and a non-transitory machine (a computer or thelike)-readable storage medium for storing the program. Further, theprogram may be electronically transferred by a predetermined medium suchas a communication signal transferred through a wired or wirelessconnection, and the present disclosure appropriately includesequivalents of the program.

Further, the apparatus for setting a handover parameter according to anembodiment of the present disclosure may receive the program from aprogram providing apparatus connected wiredly or wirelessly and storethe program. The program supply apparatus may include a program thatincludes instructions to execute the various embodiments of the presentdisclosure, a memory that stores information or the like required forthe various embodiments of the present disclosure, a communication unitthat conducts wired or wireless communication with the electronicapparatus, and a control unit that transmits a corresponding program toa transmission/reception apparatus in response to the request from theelectronic apparatus or automatically.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for wireless communication by a userequipment (UE), the method comprising: receiving, from a base station(BS), first information including a list of cells associated with afirst time-to-trigger (TTT) and second information including at leastone physical cell identity range associated with the list of cells;receiving, from the BS, third information including a value of the firstTTT and a value of a second TTT; and transmitting, to the BS, ameasurement report for a first cell based on the value of the first TTT,the first cell being included in the at least one physical cell identityrange.
 2. The method of claim 1, further comprising: transmitting, tothe BS, a measurement report for a second cell based on the value of thesecond TTT, the second cell being not included in the at least onephysical cell identity range.
 3. The method of claim 1, wherein thefirst information and the third information are received through a radioresource control (RRC) reconfiguration message.
 4. The method of claim3, wherein the first information is in a MeasObjectEUTRA informationelement (IE) in the RRC reconfiguration message.
 5. The method of claim3, wherein the third information is in a ReportConfigEUTRA informationelement (IE) in the RRC reconfiguration message.
 6. A method forwireless communication by a base station (BS), the method comprising:transmitting, to a user equipment (UE), first information including alist of cells associated with a first time-to-trigger (TTT) and secondinformation including at least one physical cell identity rangeassociated with the list of cells; transmitting, to the UE, thirdinformation including a value of the first TTT and a value of a secondTTT; and receiving, from the UE, a measurement report for a first cellbased on the value of the first TTT, the first cell being included inthe at least one physical cell identity range.
 7. The method of claim 6,further comprising: receiving, from the UE, a measurement report for asecond cell based on the value of the second TTT, the second cell beingnot included in the at least one physical cell identity range.
 8. Themethod of claim 6, wherein the first information and the thirdinformation are transmitted through a radio resource control (RRC)reconfiguration message.
 9. The method of claim 8, wherein the firstinformation is in a MeasObjectEUTRA information element (IE) in the RRCreconfiguration message.
 10. The method of claim 8, wherein the thirdinformation is in a ReportConfigEUTRA information element (IE) in theRRC reconfiguration message.
 11. A user equipment (UE), the UEcomprising: a transceiver; and a controller coupled to the transceiver,wherein the controller is configured to: receive, from a base station(BS), first information including identifier list of cells associatedwith a first time-to-trigger (TTT) and second information including atleast one physical cell identity range associated with the lest ofcells, receive, from the BS, third information including a value of thefirst TTT and a value of a second TTT, and transmit, to the BS, ameasurement report for a first cell based on the value of the first TTT,the first cell being included in the at least one physical cell identityrange.
 12. The UE of claim 11, wherein the controller is furtherconfigured to transmit, to the BS, a measurement report for a secondcell based on the value of the second TTT the second cell being notincluded in the at least one physical cell identity range.
 13. The UE ofclaim 11, wherein the first information and the third information arereceived through a radio resource control (RRC) reconfiguration message.14. The UE of claim 13, wherein the first information is in aMeasObjectEUTRA information element (IE) in the RRC reconfigurationmessage.
 15. The UE of claim 13, wherein the third information is in aReportConfigEUTRA information element (IE) in the RRC reconfigurationmessage.
 16. A base station (BS), the BS comprising: a transceiver; anda controller coupled to the transceiver, wherein the controller isconfigured to: transmit, to a user equipment (UE), first informationincluding identifier list of cells associated with a firsttime-to-trigger (TTT) and second information including at least onephysical cell identity range associated with the list of cells,transmit, to a user equipment (UE), third information including a valueof the first TTT and a value of a second TTT, and receive, from the UE,a measurement report for a first cell based on the value of the firstTTT, the first cell being included in the at least one physical cellidentity range.
 17. The base station of claim 16, wherein the controlleris further configured to receive, from the UE, a measurement report fora second cell based on the value of the second TTT, the second cellbeing not included in the at least one physical cell identity range. 18.The base station of claim 16, wherein the first information and thethird information are transmitted through a radio resource control (RRC)reconfiguration message.
 19. The base station of claim 18, wherein thefirst information is in a MeasObjectEUTRA information element (IE) inthe RRC reconfiguration message.
 20. The base station of claim 18,wherein the third information is in a ReportConfigEUTRA informationelement (IE) in the RRC reconfiguration message